Presentation 57th Annual Conference of the Particle Therapy Co-operative Group (PTCOG57)

Mizuno, Hideyuki

For multicenter clinical studies of carbon-ion radiation therapy (C-ion RT), dose uniformity among centers is crucial. In the clinical studies of The Japan carbon-ion radiation oncology study group (J-CROS), dosimetric inter-comparison for all centers participating in clinical studies was performed using the end-to-end test method. All five centers that had performed C-ion RT in Japan, in 2017, participated. A dedicated water phantom was produced for the test. CT imaging and treatment plan was performed using the same method as the patient, the physical dose of the isocenter was measured by the ionization chamber dosimeter, and compared with the calculated dose from the treatment planning system. As a result, the difference between the measured and calculated doses in all five facilities were within ± 3%, tolerance level. Uniformity of dose among institutions is guaranteed. In addition, in response to the inter-comparison dosimetry, some centers have begun actions to improve the dosimetry precision. For instance, thermometers and barometers used for absolute dosimetry in one center, that had not been calibrated as those were mounted in the irradiation system, were finally calibrated. In other center, old type ionization chamber was used as the reference dosimeter, but it was updated to a new type. The team of medical physicists of J-CROS continue for these kinds of QA activity among C-ion RT centers.

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